Holding tanks of the type mentioned above are known as a matter of principle in various embodiments and are used in sanitary installations, for example, especially in portable sanitary installations. Portable sanitary installations are set up for a certain period of time at events such as trade fairs and at construction sites or the like and later transported away again. The sanitary installations or the portable sanitary installations usually cannot be easily connected to a wastewater system or to the sewage system at the site, for which reason they are often equipped with a holding tank. In the holding tanks that are known from practice, however, it has proven to be disadvantageous that these tanks reach a high fill level relatively quickly as a result of receiving fecal matter and flushing water or flushing fluid from the sanitary fixtures and must therefore be emptied relatively frequently on-site by qualified personnel.
In principle, it is also already known and environmentally advantageous to reuse the liquid collected in the holding tank as flushing water or flushing fluid. Appropriate filters and suction devices are used for this purpose. In practice, this often results in the problem that the suction devices provided in or on the holding tanks are clogged by the solid components in the holding tank and/or of solid components and suspended particles being sucked up as well. In addition to the feces themselves, these solid constituents may also include toilet paper, paper towels, or the like that get into the holding tank. As a result, suction is impaired or the extraction system damaged, resulting in commensurately high maintenance. So far, no satisfactory solution has been found that enables a holding tank or a sanitary installation with such a holding tank to be used for a sufficient period of time without intermediate emptying or maintenance by qualified personnel. Another frequent drawback of the sanitary installations and portable sanitary installations that are known from practice and equipped with a holding tank is limited flexible applicability, since the sanitary installations usually require an external power supply, particularly if pumps are used to reuse the liquid from the holding tank. A need for improvement exists in this regard.